THE OPEN-HEARTH FURNACE.
SECTION Villa.—Description of a .regenerative- furnace.—The open-hearth process consists in melting pig-iron, mixed with more or less wrought-iron, steel., or similar iron products, by exposure to the direct action of the flame in a regenerative gas furnace, and converting the resultant bath into steel, the operation, being so conducted that the final product is entirely fluid.
Regeneration is specified, because it is impracticable to obtain the necessary temperature in any other way. The construction of melting furnaces varies1 in every place, but in all of them the general principles are the same. Where natural gas is used, the fuel is not regenerated, but the air is always preheated. The following description will assume that both gas and air undergo the same treatment. In Fig. VIII-A is given a drawing of a common type of furnace; its faults will be discussed later, but it will illustrate the method of operation. The gas enters the chamber F, which is surrounded by thick walls and filled with brickwork so laid that a large amount of heating surface is exposed, while, at the same time, free passage for the gas is assured. The air enters a similar chamber, E. In starting a furnace, the bricks in these chambers are heated before any gases are admitted. With rich fuels, like natural gas, this may not- be essential, but ordinary producer gas, when cold, can hardly be burned with air at the ordinary temperature, and an attempt to do so may result in serious explosions, so that it is advisable to heat the furnace by a wood fire until the regenerators show signs of redness. When, finally, the gas and air are admitted, precautions are taken to avoid explosions by filling the passages with the waste gases from the wood fire.
The first effect of their entrance is to cool the chambers on the incoming end, for no heat is produced until they meet in the port at 0. From this point the flame warms the furnace and also the